1. Field of the Invention
This invention relates to an improved drill pipe coupling of simple yet highly effective construction which has numerous advantages including ease of attachment/detachment of hollow pipe sections, watertightness, and secure attachment of hollow multiple pipe sections regardless of direction of pipe rotation. More particularly, it is concerned with a pipe coupling having a male/female connection which prevents rotation of hollow separate pipe sections with respect to each other, with means for preventing the connection from being pulled apart, and means for water tight sealing of the coupling and pipe section for water flowing within the pipe sections and the coupling at high pressure.
2. Description of the Prior Art
When drilling or boring through earth it is often necessary to couple multiple lengths of pipe together in order to drill the required length as by using a drilling or augering accessory of the type disclosed in Van Gundy U.S. Pat. No. 4,197,033. Often pressurized water is introduced at one end of such a pipe string and is exited at the tip of an auger at the other end. This pressurized water irrigates the flighted auger and actually helps breakup the earth to be excavated which helps prevent the need to back the auger out and redrill. It is possible for the water pressure in this type of drilling to reach or exceed pressures of 3000 psi. As can easily be understood, any water leakage at the pipe couplings will result in loss of pressure at the auger tip which in turn reduces the effectiveness of the drilling operation.
The longitudinal and rotational coupling of drill pipe is well known. It is known to use various pins and interlocking configurations to prevent the separation of coupled pipe sections. For example, Davis British Patent No. 1,030,984, discloses an elongated box having a longitudinal bore which is irregular in cross sectional shape and a communicating end portion of which is circular in cross section and a mating elongated tubular pin, the external size and cross sectional configuration of which is complemental to the size and cross sectional configuration of the bore in the box. The pin thus slidably but nonrotatably fits into both the above mentioned bore portions of the box. There is an annular external keeper groove encircling the pin intermediate its ends, an aperture extending transversely through the wall of the box at a location to align with the groove when the pin and box are mated, and a removable keeper insertable into the aligned aperture and groove to lock the pin and box against longitudinal separation. A conventional O-ring sealing member seals against the wall of the circular cross section bore portion of the box when the pin and box are mated.
There is no discussion in the Davis patent of any flow through the coupled drill pipe. Though the hollow construction might be presumed to allow such flow, there is no indication that such a coupling would provide a water tight seal at the pressures contemplated by the present invention.
A sucker rod coupling is disclosed by Sutton et al U.S. Pat. No. 1,658,264. The coupling disclosed in this patent has structure providing for a pin to couple two parts, each connected to corresponding rods. There is no disclosure for accommodating water flow therein as in the present invention.
A pipe and hose coupling is disclosed by Chapin U.S. Pat. No. 221,153. The patent discloses a U-shaped locking-key that enters recesses of mated male and female portions and is retained by side caps of the female portion. Again, there is no indication that a water tight seal is provided at the required pressures.
A number of coupling arrangements have been proposed in the past for drill pipe strings. In general however, these coupling schemes have not met the need for providing a reliable, yet water tight coupling of pipe sections at the required pressures.